1. Field of the Invention
The invention relates to a process for lowering the mineral (ash) content and increasing the nutritional value of sea algae and halophytes, to the product produced by such process, and to use such product as or in feed or food.
2. Background
There is little food value in the complex nitrogenous and carbohydrate compounds found in algae because humans' digestive system cannot break down these complex structures into useful metabolites during digestion. Algae do have value as roughage, however. The mineral, vitamin, and iodine content of algae provide valuable nutrients. [Encyclopedia Britannica, Macropaedia, Vol. 1, (1974), page 489] Palatable and digestible types of sea algae as food sources for humans would be desirable. Seaweeds, usually in meal form from drying and grinding, are eaten in relatively small amounts by some domesticated commercial animals as part of their diet as seaweeds do not provide the animals with a balanced diet. It seems that digestibility in animals depends upon the sea algae source and the health of the animals. The principal seaweeds consumed by animals are rockweed (Fucus and Ascophyllum) and Laminaria species are also used.
Dulse (texture of this rubber) is commonly dried and eaten by North Atlantic fishermen, and also eaten with fish and butter, boiled with milk and rye flour, or as a relish. Sea lettuce is sometimes used in soups. Laver, especially Porphyra tenera, is used in a variety of foods.
Although this invention deals only with the extraction of mineral matter from algae and halophytic plants and does not involve the extraction of various alginates, agar or carrageenans, the following references are cited inasmuch they refer to processes involving sea algae.
In essence, agar is a polymer of carbohydrate prepared from certain sea algae, e.g., some species of red algae or seaweeds. Agar is often used as a vegetarian gelatin substitutes (e.g., in soups, sauces, jellies and ice cream). It also finds use in icings, glazes, cookies, meringues, confectionery, pie fillings, piping gels, canned meat and fish.
Agar is extracted from various varieties of red algae, principally from species of Gelidium, Gracilaria, Pterocladia, Acanthopeltis and Ahnfeltia. The first two are sea weeds. Agar is extracted from sea algae by means of hot water. [Encyclopedia Britannica, ibid., page 89] In more detail, agar (or agar-agar) is prepared by boiling, purifying and drying sea algae to an amorphous and translucent product (usually put into a powder, flake or brick form). [Encyclopedia Britannica, ibid.] Agar is extracted from red algae and then purified. [Agar, Oregon State University, (http://food.oregonstate.edu/gums.agar.html), (Aug. 08, 2003 AOL), Update Jul. 14, 2003, two pages]
Carrageenans are naturally occurring linear sulfated polysaccharides which occur in certain species of red seaweed (Rhodophycae) of the Solieriaceae, Gigartinaceae, Furcellariaceae, Phyllophoraceae, Hypneaceae, Rhabdoniaceae , and Rhodophyllidaceae families. Carrageenan is extracted from various species of red algae. Carrageenan extract is removed from Irish moss by boiling dried Irish moss. [Encyclopaedia Britannica, Micropaedia, Vol. V, (1974), page 426] What Is Carrageenan?, Tacara, (http://www.tacara.com.my/articles/carrageenan%20article1.htm), (Aug. 08, 2003 AOL), four pages, states:                “The main carrageenan types, lambda, kappa and iota, can be prepared in pure form by selective extraction techniques.”        “In 1884, the first successful extraction of carrageenan from Chondrus crispus was attributed to Schmidt, followed by a patentable process of extraction by alcohol precipitation. The production of carrageenan is a straightforward operation consisting of extraction, purification and isolation. The seaweed should be cleaned to remove any sand before extraction proceeds. Alkaline conditions are necessary to modify the galactan structure, resulting in better gelling ability. Modifications as well as differences in extraction techniques exist. Three processes are most commonly used: alcohol precipitation, freeze-thawing and gel press.”        “What is semi-refined/Philippines Natural Grade (PNG) carrageenan?”        “This form of carrogeenan evolved into a food ingredient from a past that began as a way of treating raw Eucheuma seaweed in the Philippines prior to export . . . developed in the Philippines a pre-treatment process for the raw seaweed which yielded the item of commerce now called ‘alkali treated cottonii chips’. A powder made from these chips was developed in the early 1970s for use by manufacturers of canned pet food. The performance properties of the alkali modified flour approached those of refined carrageenan . . . ”        “The PNG process parallels the refined carrageenan process, except for the extraction step. In making refined carrageenan, the polysaccharide is extracted or dissolved from the seaweed to yield a carrageenan solution at a concentration of about two weight percent. PNG uses a reverse extraction process where impurities are extracted from the seaweed, and the polysaccharide is left in a gel state containing about 45 weight percent carrageenan and algal cellulose. PNG differs from refined carrageenan primarily in its relatively high algal cellulose content and lower salt content.” [Pages 2 and 3]The article makes no mention of the use of an acid. On the contrary, the article mentions the necessity of maintaining basic conditions for its purposes.        
AisonsChem, (http://www.aisonschem.com.cn/carrageenan.htm), (Aug. 08, 2003 AOL), eleven pages, (Copyright 2003), states:                “Carrageenan is extracted from the raw material with water at high temperatures. The liquid extract is purified by centrifugation and/or filtration. The liquid extract may be converted into a powder by simple evaporation of water to yield the so called drum dry carrageenan.”[Page 2]        
Algin, broadly, are various colloidal substances extracted from brown marine algae. Algin is commercially obtained from Fucus, Ascophyllum nodossum, Laminaria and Macrocystis. Algin is obtained by digesting seaweed [sea algae] in alkali and precipitating either the calcium salt or alginic acid.
Algin herein refers specifically to soluble sodium alginate. However, algin, in a broader sense refers to alginic acid or salts of alginic acid—one has to look at the context to ascertain which meaning is being used.
Schenck, K., Wound dressings (1): Calcium alginates for moist wound treatment, WundForum Wound Care, (Aug. 10, 2003 AOL), seven pages, states:                “The manufacturing process of alginates involves crushing and washing of the raw material and dissolution of the extracted sodium alginate in water. A viscous solution is obtained which is extruded into a calcium chloride bath. hence, the sodium ions are replaced by calcium ions and the insoluble calcium alginate is precipitated.” [Page 2]Jork, A., et al. Appl. Microbiol. Biotechnol., (2000), 53:224–229, disclosed extracting alginate from the kelp Laminaria pallida using Na2CO3 in EDTA.        
Marinalg Welcome, (http://www.marinalg.org/products/algina_inf.htm), (Aug. 08, 2003 AOL), two pages, states:                “Alginates are extracted from various species of brown seaweeds (Phaecohyceae) by a multi-step process. A typical extraction process involves first washing and treating seaweed with diluted sulfuric acid (quantitatively transforming calcium alginate into alginic acid), extraction by dissolution with alkali, separation of insolubles, then precipitation as the calcium salt, followed by acid washing to recover alginic acid. The salts and esters of alginic acids are obtained by neutralization and esterification, respectively.”Marinalg Welcome also states that algin is sometimes used in the literature for the term alginates and that alginates includes alginic acid, salts of alginic acid (sodium, potassium, ammonium, magnesium and calcium alginates) and esters (propylene glycol aginate). The e-document also states that alginates are used in a variety of human and pet foods.        
Truus, Kalle, et al., Proc. Estonian Acnd. Scr. Chem., (2001), 50, 2, 95–103, states:                “In principle, the isolating process of alginates from brown algal biomass is simple, including stages of pre-extraction with hydrochloric acid (□ alginic acid), followed by washing, filtration, and neutralization with alkali (□ sodium alginate). Sodium alginate is precipitated from the solution by alcohol (isopropanol or ethanol) and usually re-precipitated (to achieve higher purity) in the same way [9]. However, the real processing scheme for alginate production is quite complicated, including 15 steps [10].” [Page 96]        “Extraction and precipitation of alginates. In all cases, alginates were isolated from the seaweeds in sodium form. Algae were processed at three principal regimes: (a) “cold” method, (b) “hot” method, and (c) modified method including extraction in boiling state.        (a) Cold method. 20 g of air-dry algae was stored (18 h) in 300 mL of 1% CaCl2 solution at room temperature. After that, the seaweeds were washed with water (3×300 mL), stored (1 h) in 5% solution of hydrochloric acid, and washed again with water (3×300 mL). Then algae were treated with 3% Na2CO3 solution (100 mL, 1 h) and water (300 mL) was added to stand overnight. The viscous mixture was filtered and the sodium alginate formed was precipitated from the solution by adding isopropanol (1:4 v/v). The precipitate was filtered, washed by isopropanol, and dried in air.        (b) Hot method. The seaweeds were treated as described above (method a) with the only difference that the storing time was 3 h and the processing temperature was 50° C.        (c) Modified method. 20 g of air-dry algae was treated with boiling water (300 mL, 30 min) and with 0.5% CaCl2 solution (300 mL, 100° C., 30 min). The extract was separated and the algal residues were treated with 0.5% NaCl solution (300 mL, 1 h) at 100° C. The dark-colored extract was removed and 3% Na2CO3 solution (100 mL, 100° C.) was added to the seaweeds by intensive stirring (30 min, a boiling water bath). Then, additional 100 mL of water was added and the mixture was filtered. Sodium alginate was precipitated from the solution as described above.” [Page 98]        
Training Manual On Gracilaria Culture And Seaweed Processing In China, Chapter III (Cont.), (http://www.fao.org/docrep/field/003/AB730E/AB730E04.htm), (Aug. 10, 2003 AOL), 21 pages, states:                “Pretreatment: The alginophytes (Laminaria sp.) are treated, first, with 0.1–0.4% commercial formallin solution at room temperature for several hours to fix the pigments together with the phenolic substances present in the thalli diminishing the coloration of the extracted liquor. Then the thalli are soaked with dilute acid such as 0.1 M H2SO4 or HCl solution for 30 minutes at room temperature to convert the metallic salts of alginate into alginic acid.”        “Hot extraction: The treated wet thalli are extracted with 1% sodium carbonate solution . . . ” [Page 12]The above quotation describes the start of the manufacture of sodium alginate from sea algae by the calcification process.        
There is no admission that the literature and other art described and/or quoted above and below are prior art to this application or the invention described in this application.